Hydraulically controlled grab



June 19 1962 A. NIMESKERN HYDRAULICALLY CONTROLLED GRAB Filed June 1. 1959 INVENTOR AUGUSTE NiME K ERN United States Patent 3,039,812 HYDRAULICALLY CONTROLLED GRAB Auguste Nimeskern, Ave. Prud Homme Havette, Etain, Meuse, France Filed June 1, 1959, Ser. No. 817,130 Claims priority, application France June 18, 1958 Claims. (Cl. 294-88) This invention relates to grabs and grab buckets which comprise a number of claws or segments or equivalent members articulated generally around the axis of a shell or body carried by some form of hoisting or lifting apparatus. The opening and closing of the members is controlled either mechanically or hydraulically but in the known apparatus the actuating mechanism is common to the various members; thus the motion of the latter is necessarily coupled or combined. As a result, on closure, the stopping of two opposite claws or segments or equivalent members stops the entire closing motion; the members which have been first to seize the material to be hoisted are then subjected to excessive strain while the other members remain inoperative.

The invention provides a grab or grab bucket by which this drawback is remedied. In accordance with the invention, each claw or segment or equivalent member is controlled during its closure by an individual jack whereas a common jack actuates all said members on opening. As a result the closing motion of any particular member is not arrested until said member has made contact with the material and exerts on the latter a grip corresponding to the hydraulic pressure acting on its jack. All the members are operative and none is exposed to the risk of excessive fatigue.

The invention will now be further described with reference to the accompanying drawing which shows an hydraulically operated grab with claws in accordance with the invention.

FIG. 1 represents an axial section of the grab with the claws in the fully closed position.

FIG. 2 represents an axial section in the plane lI-Il of FIG. 1, only the front claw being shown.

FIG. 3 is a view corresponding to FIG. 1 but with the claws in the open position.

The shell or body of the grab consists of a tube 1 closed by an upper plate 2. If the grab is designed to be suspended from the chain of a hoisting apparatus, two lugs 3 welded on said plate 2 form a fork in which the lowest link 4 of the suspension chain is articulated on a pin 5. At its lower end the tube 1 has an outer flange 6 on which are welded, for each claw 9, two lugs 7, 7 together forming a protruding fork in which the claw is articulated on a pin 8 on the outside of the flange. The grab shown comprises four claws 9 arranged symmetrically around the axis of the tube 1. Each of these claws is integral with a radial arm 10 which, in the fully closed position of the claws, lies flush against the flange 6 and which, passing through the corresponding fork 7, 7 is pivoted at its centre on a pin 8.

Each claw arm 10 projects inwardly in front of the open end of the tube 1 to within a short distance of the axis of the latter and has welded on its inner end surfaces two small bars 11 extending at right angles to it and forming a fork equipped with a small roller 12. The base 13 of a piston 14 slidable in the tube 1 can act on the pulley assembly 12. This piston is attached to the lower end of the plunger 15 of a jack mounted in the tube 1. The base of the plunger cylinder 16 of this jack carries a yoke 17 which is pivoted on a transverse pin 18 passing through two interfacing lugs 19 welded on the inner wall of the tube 1.

In a notch cut in the elbow of each claw 9 and its arm 10 a pin 29 articulates the outer end of the plunger ice 21 of a jack associated only with said claw. The base of the cylinder 22 of this jack carries a lug 23 which is pivoted on a pin 24 passing through two lugs 25 welded on the tube 1 and forming a hinge for the jack.

All the jacks are connected to a conventional hydraulic distributor (not shown) which permits distribution either to the central jack cylinder 16 or, in parallel the one to the others, to the Various individual jack cylinders 22. When these latter jack cylinders are connected to exhaust, the hydraulic pressure of the central jack 16, .15 causes the descent of the piston 14 which, pushing down the pulleys 12, causes the claws 9 to pivot to the opening position (FIG. 3) while returning the pistons 21 of the individual jacks 21, 22. On the other hand, when the central jack cylinder 16 is connected to exhaust, and the hydraulic pressure is applied to the individual jack cylinders 22, the jack plungers 21 cause the claws 9 to pivot about the pins 8 towards the closing position.

As the same degree of force is applied to each claw, all the claws close symmetrically, as long as no obstacle is encountered. When two opposite claws are stopped by the resistance of a body they have gripped, the others continue their closing strokes until they themselves are brought to a halt for the same reason or are fully closed. Thus all the claws are operative and no single one of them is exposed to the risk of experiencing excessive fatigue, the fatigue strain being restricted to the gripping force furnished by each individual jack, to support which the claw has been designed. It will be noted that the fully closed position is delimited by the pressure of the arms 10 lying flush against the flange 6.

The invention is applicable to grab buckets as well as to grabs with claws, irrespective of the type of hoisting apparatus of which it forms a part. The invention is not restricted to the embodiment described and illustrated constructional modifications Within its scope being possible as will now be understood.

I claim:

1. A grab comprising a body, a plurality of gripping members each pivotally mounted on said body to turn from an open to a closed position and in varying degree to partially closed positions between said open and closed positions, an individual jack operatively connected to each of said gripping members to turn the member toward said closed position until the member encounters a portion of the body to be gripped and is stopped in a partially closed position, and a common jack engageable separately with each of said gripping members whether in closed or partially closed positions of different degree to move the members toward their open positions.

2. An hydraulically controlled grab comprising a tubular body open at its lower end, a plurality of gripping members each pivotally mounted on said body to turn from an open to a closed position and in varying degree to partially closed positions between said open and closed positions, an individual hydraulic jack operatively connected to each of said gripping members to turn the member toward said closed position until the member encounters a portion of the body to be gripped and is stopped in a partially closed position, each of said gripping members having an arm extending in front of the open lower end of said tubular body in both the open and closed position of the member, a piston slidably mounted in said tubular body and engageable separately with each of said arms when the gripping members are in closed and partially closed positions of difierent degree, and a further hydraulic jack engaging said piston so that actuation of said piston by said further hydraulic jack causes the opening of all said gripping members.

3. A hydraulically controlled grab as claimed in claim 2, comprising a roller mounted on each of said arms and engageable by said piston.

4. A hydraulically controlled grab as claimed in claim 2, comprising an outer flange at the open lower end of said tubular body, forks projecting laterally beyond said flange, each of said arms being pivotally mounted in one of said forks and lying flush against said flange when the corresponding gripping member is in its fully closed position.

5. A hydraulically controlled grab as claimed in claim 2', wherein each of said individual jacks is hingedly connected in the plane of its corresponding gripping member, at one end to the outer Wall of said tubular body and at the other end to a point on the outside of said gripping member.

References Cited in the file of this patent UNITED STATES PATENTS Billings Sept. 15,

Troyer July 31,

Larson Dec. 2,

Stedt Mar. 17,

Shook Sept. 8,

FOREIGN PATENTS Germany Feb. 28, 

